Ladder code doesn´t work. Why is it ?

[giovani]

Thanks again guys !!!

Unfortunalely for me I won´t be able to deal with this problem for the next two or three weeks because it was needed to run the actual automation system so that a test can be done in the hyperbaric chamber. That´s why I can´t verify the feedback you gave me before answering this post, 93lt1, and following your sugestion Rube.

I´ll answer the questions posted by you 93lt1 and, when I can test the program in the PLC I´ll post a new message here.


"Are you saying that when you toggle N7:18/1, B3/320 comes on, and in rung 53 turns on O:18/4? Does O:18/4 turn on in RSLogix?"

That´s the problem. When N7:18/1 is toggled and B3/320 is turned true, O:18/4 is not turned on, although I:14/2, I:13/5 and O:18/5 allow rung continuity.

"You are running the logic in a SLC aren't you? Is the SLC in Run mode (or REMRUN)?"

Yes, the SLC is in Run mode.

"Is the Pump motor starter wired to the correct output?"

Yes, it is. I´m only designing a new automation system which will use the same inputs and outputs of the old one. All the inputs and outputs of the system were already wired.

Thanks a lot !!!

 

[93lt1]

That´s the problem. When N7:18/1 is toggled and B3/320 is turned true, O:18/4 is not turned on, although I:14/2, I:13/5 and O:18/5 allow rung continuity.

So you see this: ???

 

[Rube]

If he does see that, the output O:18/4 is used LATER in the logic and the conditions ahead of that output are false (although a "Find All" in his posted logic didn't show the output anywhere else).

 

[giovani]

That´s it, 93lt1 !!

See Rube ? That´s pretty strange at first, isn´t it ? The output O:18/4 is only used once in all the ladder, so, if there´s rung continuity, it should be set to true, shouldn´t it ?

Today I´ll be able to do quick test and see if I can find something. But the probleam is that, since the test under execution in the hyperbaric chamber had to be temporally stopped - and the hyperbaric chamber is open right now ! - I won´t be able to test the code using the original inputs and outputs so I´ll replace them with unused bits.
Doing this test I think I can see if the logic works just fine.

I´ll post a message here to let you guys know about the results.

Thanks !!!

 

[jshiepe]

Giovani,

Check your program to be sure that the 16-bit output card is not being addressed as an entire word elsewhere. Look for sequencer instructions or other file type instructions like COP and FLL. One quick way to tell is if you open up the output table and see a "W" for O:18.0, you know that there is an instruction somewhere that is controlling the entire card at once.

Hope this helps,
Jeff

EDIT: Sorry guys....jumped to the last post after not visiting this thread in a couple days. OOPS!

 

[jshiepe]

OK.....so after my brain f*&t cleared and I downloaded the code, the only thing that comes to mind that hasn't been mentioned yet is whether there is an HMI attached to this PLC that may have control of the output directly, like a maintained pushbutton directly addressing the output rather than a permissive bit. Along those same lines of thinking, are there other PLC's in this system that may have control of the output through messaging?

Just a thought....

Jeff